i = 0
while i < 3 :
    username = input('username:')
    password = input('password:')
    if username != "abc" :
            print("Wrong username or password")
    elif password !="abc":
            print("Wrong username or password")
    else:
            print("welcome") 
            break
        
    i+= 1

# 来个错误次数提示？